Blood vessel morphometry in human colorectal lesions

Abstract

Neovascularisation in tumours of different cell origins has been well documented qualitatively. In this report, we have assessed vascular architecture in different pathological lesions of the colorectum by quantifying blood vessel parameters in order to detect subtle morphological changes using objective methods. Colorectal tissue samples were obtained from resected large bowels containing malignant tumours. Biopsies were taken from defined sites in the resected specimen and were classified as normal (N), potentially premalignant mucosa (PPM), adenomatous polyp (P) and adenocarcinoma (ADCA). All tissues were fixed in modified Karnovsky's fixative for 4 hrs and postfixed in 1% OsO4 for 1 hr. Samples were processed for EM under standardized procedures and embedded in Epon. 0.5 μm semithin sections from five patients per group were stained with toluidine blue. A multistage systematic sampling procedure was adopted. The inner outlines of all blood vessels in the lamina propria (LP) were digitised using a Zeiss VIDAS Image Analyzer at a final magnification of x 1,050. The area of the reference (LP) was also measured. No attempt was made to distinguish between the different types of vessel. The morphometric blood vessels parameters quantified were volume density (V(v)), numerical density (N(A)), length density (L(V)) and mean transverse sectional area (A). Statistically significant differences in Vv and A were detected between all groups except between N and PPM and between P and ADCA. No significant differences in N(A) and L(V) were present in any group comparisons. The mean values of all parameters were the highest in ADCA. Our results suggest that vasodilatation occurred in order to provide an increased supply of nutrients to support active growth and division of the transforming cells. Such vasodilatation might also reflect the inflammatory response to the presence of actively growing malignant cells since activated immune cells are able to release vasoactive substances.